Here, we demonstrate that the Mu variant is highly resistant to sera from COVID-19 convalescents and BNT162b2-vaccinated individuals. Direct comparison of different SARS-CoV-2 spike proteins revealed that Mu spike is more resistant to serum-mediated neutralization than all other currently recognized variants of interest (VOI) and concern (VOC). This includes the Beta variant (B.1.351) that has been suggested to represent the most resistant variant to convalescent and vaccinated sera to date.
Based on the latest round of assessments, B.1.621 was classified as a VOI on 30 August 2021 and given the WHO label “Mu”. This includes the descendent Pango lineage B.1.621.1. This variant is known as 21H in Nextstrain nomenclature. The Mu variant has a constellation of mutations that indicate potential properties of immune escape. Preliminary data presented to the Virus Evolution Working Group show a reduction in neutralization capacity of convalescent and vaccinee sera similar to that seen for the Beta variant, but this needs to be confirmed by further studies.
Since its first identification in Colombia in January 2021, there have been a few sporadic reports of cases of the Mu variant and some larger outbreaks have been reported from other countries in South America and in Europe. As of 29 August, over 4500 sequences (3794 sequences of B.1.621 and 856 sequences of B.1.621.1) have been uploaded to GISAID from 39 countries. Although the global prevalence of the Mu variant among sequenced cases has declined and is currently below 0.1%, the prevalence in Colombia (39%) and Ecuador (13%) has consistently increased. The reported prevalence should be interpreted with due consideration of sequencing capacities and timeliness of sharing of sequences, both of which vary between countries. More studies are required to understand the phenotypic and clinical characteristics of this variant. The epidemiology of the Mu variant in South America, particularly with the co-circulation of the Delta variant, will be monitored for changes.
Carlos Migoya, CEO of Jackson Health, revealed that now 10% of COVID-positive patients whose results are being sequenced at the University of Miami’s pathology lab have a strain [B.1.621] that originated out of Colombia.
“And here’s a real shocking thing that’s spreading in Colombia quite a bit,” Migoya told Local 10 News. “And they haven’t seen it anywhere else outside of Colombia. Well, guess what? In the last week, 10% of our patients had the Colombian variant.” (July 26th 2021)
In this study, we reported the emergence and spread of the novel B.1.621 lineage of SARS-CoV-2, a new VOI with the insertion 146N and several amino acid substitutions in the Spike protein (T95I,Y144T, Y145S, R346K, E484K, N501Y and P681H). Although B.1.621 does not meet all of the VOC classification criteria so far, the set of mutations gathered the Spike protein could confer a synergistic impact on attributes such as reduction of vaccine-induced protection from severe disease, increased transmission and disease severity
During the past two weeks, 7 residents of a care home near Zaventem in Belgium have died after having contracted the B.1.621 variant of coronavirus first identified in Colombia, South America. All those that have died at the care home had been fully vaccinated against coronavirus.
On 16th July, two coronavirus infections were confirmed at the Ter Burg care home. As soon as the first infections were confirmed those in charge at the home put the afflicted section under quarantine. A total of 20 residents tested positive. As measures had been taken the outbreak was contained in the section of the home where it had started.
Nevertheless, 7 of the 28 residents with advanced dementia have passed away. Some of these were in poor physical health to start with. One of them was terminally and another was being given palliative care. However, some of those that died were in relatively good physical health.
Interestingly, the UK PHE have just released a threat assessment for B.1.621, reprinted below, and there are some recent posts from their Twitter account.
This variant was blamed for the rapid growth in Colombia 🇨🇴 in June/July
(at that time Alpha was dominant, almost no Delta) pic.twitter.com/EXwut4WgqL
— Meaghan Kall (@kallmemeg) August 6, 2021
In a possibly related development, Belgium has decided to lift its ban on travel from countries with high levels of coronavirus infections
We report the emergence of a novel lineage of SARS-CoV-2 in South America, termed C.37. It presents seven nonsynonymous mutations in the Spike gene (Δ247-253, G75V, T76I, L452Q, F490S, T859N) and a deletion in the ORF1a gene (Δ3675-3677) also found in variants of concern (VOCs) Alpha, Beta, and Gamma. Initially reported in Lima, Peru, in late December 2020, it now accounts for 97% of Peruvian public genomes in April 2021. It is expanding in Chile and Argentina, and there is evidence of onward transmission in Colombia, Ecuador, Mexico, the USA, Germany, and Israel. On June 15, 2021, the World Health Organization designated C.37 as Variant of Interest (VOI) Lambda.
Here we report a novel and highly divergent lineage with 21 characteristic mutations, including 10 non-synonymous, 8 synonymous and 3 mutations in non-coding regions (5’and 3’ UTR and intergenic region).
Four Colombian sequences collected between December 26, 2020 and January 14, 2021with a characteristic mutation pattern, including two amino acid changes in the Spike protein (L249S and E484K) were assigned to the B.1.111 lineage